/*
 * http://blog.csdn.net/weed_hz/article/details/9787163
 */

#include <linux/miscdevice.h>
#include <linux/delay.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/types.h>
#include <linux/delay.h>
#include <linux/moduleparam.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/ioctl.h>
#include <linux/cdev.h>
#include <linux/string.h>
#include <linux/list.h>
#include <linux/pci.h>
#include <linux/gpio.h>


#define DEVICE_NAME "mymap"


static unsigned char array[10]={0,1,2,3,4,5,6,7,8,9};
static unsigned char *buffer;


static int my_open(struct inode *inode, struct file *file)
{
    return 0;
}


static int my_map(struct file *filp, struct vm_area_struct *vma)
{
    unsigned long page;

    unsigned char i;

    unsigned long start = (unsigned long)vma->vm_start;
    unsigned long end =  (unsigned long)vma->vm_end;
    unsigned long size = (unsigned long)(vma->vm_end - vma->vm_start);


    //得到物理地址
    page = virt_to_phys(buffer);

    //将用户空间的一个vma虚拟内存区映射到以page开始的一段连续物理页面上
    if(remap_pfn_range(vma, start, page>>PAGE_SHIFT,size,PAGE_SHARED))    //第三个参数是页帧号，由物理地址右移PAGE_SHIFT得到
    {
        return -1;
    }


    //往该内存写10字节数据
    for(i=0;i<10;i++)
    {
        buffer[i] = array[i];
    }


    return 0;
}


static struct file_operations dev_fops =
{
    .owner    = THIS_MODULE,
    .open    = my_open,
    .mmap   = my_map,
};

static struct miscdevice misc =
{
    .minor = MISC_DYNAMIC_MINOR,
    .name = DEVICE_NAME,
            .fops = &dev_fops,
};

static ssize_t hwrng_attr_current_show(struct device *dev,
        struct device_attribute *attr,
        char *buf)
{
    int i;

    for(i = 0; i < 10 ; i++)
    {
        printk("%d\n",buffer[i]);
    }

    return 0;
}

static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
                   hwrng_attr_current_show,
                              NULL);


static int __init dev_init(void)
{
    int ret;

    //注册混杂设备
    ret = misc_register(&misc);

    //内存分配
    buffer = (unsigned char *)kmalloc(PAGE_SIZE,GFP_KERNEL);

    //将该段内存设置为保留
    SetPageReserved(virt_to_page(buffer));

    ret = device_create_file(misc.this_device,&dev_attr_rng_current);

    return ret;
}


static void __exit dev_exit(void)
{
    //注销设备
    misc_deregister(&misc);

    //清除保留
    ClearPageReserved(virt_to_page(buffer));

    //释放内存
    kfree(buffer);
}


module_init(dev_init);
module_exit(dev_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("LKN@SCUT");
